Systematic study of Rayleigh-Taylor growth in directly driven plastic targets in a laser-intensity range from ∼2x1014to∼1.5x1015W/cm2

Direct-drive, Rayleigh-Taylor (RT) growth experiments were performed using planar plastic targets on the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at laser intensities between similar to 2 x 10(14) and - 1.5 x 10(15) W/cm(2). The primary purpose of the experiments was to test fundamental physics in hydrocodes at the range of drive intensities relevant to ignition designs. The target acceleration was measured with a streak camera using side-on, x-ray radiography, while RT growth was measured with a framing camera using face-on radiography. In a laser-intensity range from 2 to 5 x 10(14) W/cm(2), the measured RT growth agrees well with two-dimensional simulations, based on a local model of thermal-electron transport. The RT growth at drive intensities above similar to 1.0 x 10(15) W/cm(2) was strongly stabilized compared to the local model predictions. The experiments demonstrate that standard simulations, based on a local model of electron thermal transport, break down at peak intensities of ignition designs, although they work well at lower intensities. These results also imply that direct-drive ignition targets are significantly more stable than previously calculated using local electron-transport models at peak intensities of ignition designs. The preheating effects by nonlocal electron transport and hot electrons were identified as some of the stabilizing mechanisms. (C) 2008 American Institute of Physics.